The objective of this program is to maintain approximately 100 animals (85 non-human primates, including up to 25 infant and juvenile chimpanzees and up to 60 marmosets or monkeys; and up to 25 other small animals, primarily woodchucks, but on occasion rabbits and guinea pigs) for various viral hepatitis studies. All animals will be held in cages and chamber units which will be provided by the Government. Studies which will be performed on these animals will include, but not be limited to: inoculation of the animals with various hepatitis agents, monitoring the animals for signs of disease, treating with therapeutic regimens, and collecting specimens as described by protocols furnished by the Project Officer. The studies designed by the project Officer may include: establishing infectious virus pools and/or titrating pools, testing vaccines and other immunoprophylactic agents, and determining routes of infection and the effect of antivirals and immunomodulators. The technical and professional staff of SEMA will perform the experimental protocols as provided by the Project Officer. The staff will feed, water and care for all animals as well as inoculate the primates with viral material provided by the Project Officer, collect blood and tissue samples, perform physical examinations and provide treatment, perform necropsies and other experimental procedures such as exploratory laparotomies, open liver biopsies, and lymph node biopsies. For most of the studies, it is anticipated that SEMA will perform nasal and throat swabs, intratracheal lavage, gavages, collect spinal fluids, sera, and urine, perform plasmapheresis, leukophoresis, bone marrow aspirations, needle liver biopsies, and on occasion abdominal surgery to collect up to 50 grams of liver.